Set of interrelated parts (6)
I believe the answer is:
system
'set of interrelated parts' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for system that I've seen before include "Arrangement of units in a whole" , "Method, set of connected things" , "Functioning set of interactive parts" , "Technique, method" , "Organised whole made up of related parts" .)